Method and means for the starting of synthetic yarn spinning



July 5, 1949.

J. H. BLOMQUIST METHOD AND MEANS FOR THE STARTING OF SYNTHETIC YARNSPINNING Filed May 15, 1948 INVENTOR. John Howard B/omquisf A T TORNE YPatented July 5, 1949 so STAT ES or 2,474,885 METHOUAND MEANS FfoitriiiisTAifiiN" OF'SYNTHETIC YARN'SPINNING' John Howard Blomquist,wiliriiiigtoni'Del'i, as"-' signor to E. I. du Pont de'fNemou'i's acCompamnI Wilmington, Del., a corporation of Delaware ApplicationMay 15,isisiseriaint; 27,194"

7 Claims. 1.

This invention-relates to themanufacture of artificial textilefilaments',- yarns and threads, and more particularly,- to improvementsin the dryand melt-spi'nningof synthetic filament-forming materials.

In the past, in the meltand dry-spinning of synthetic filament-formingmaterials, e. g. nylon, cellulose acetate, etc., considerable difficultyhas been experienced, when starting up a spinning -position,in obtaininguniform and equal extrusion through the orifices of the many-holedspinneretsused in'the production of continuous filament yarns.Conventionally,l the material to be spun is pumped from-a melt pool ormanifold supply system through a series offilteis orsand packs, and thenextruded; through a 'spinneret into an evaporative and/or coolingatmosphere. The evapotative or cooling atmosphere is commonly containedin a tubular structure referred toas a spinning cell. solidify byevaporation ofthesolvent, or in the case of melt-spunfilaments, bycooling, to form the continuous filaments commonly usedin the textiletrade.

Each of these spinning positions must from time to-time be shut downtemporarily; This is frequently done for the purpose of cleaning thespinnerets, the various apertures of which may become clogged. Again,some part Of the'packing-may-fail and leakages occur. Also, the filtersorspinning packs must be replaced at'frequent intervals. Therefore, atypeof preventative maintenance is usually 'followed whereby the variousspinnerets are changed at regular intervals, each change, of course,necessitating-a cessation of spinning from that particular position.

When the various parts have been cleaned or renewed andtheposit'i'onreassembled, pumping to the position to resume productionof the continuous filaments is again'started; A very considerable'difiiculty encountered in the start-up resides inthe-fact that as thepumping'starts, the spinning solution or melt is notdistributed evenlyover'the back face of the spinneret before extrusion starts. In otherwords, holes in one portion of the spinneret face startspinningbefore-holes in the other portions and the'last holes to 1 spin quitefrequently drip,-'i. e. do not-pass a continuous stream of' material, or"are slow holes, 1. e. an insufficientamoufltofmaterial is extruded toform asuitable-filament.

This difficulty is experienced with most spinnercts. Howeveiz it isespecially troublesomein the "case ofvery"large-spinnerets, i. e.200-ho1e pinnerets and larger-'(3 to 5 inches in diameter),

In this cell, the filaments of the type generally used to spin a towioroon version into staple. It can be readily seen that when certainhol'e'sin a spinneret f ace either drip 01"do-n0tf. spin 'atl *the' samerate asvthe others, corrective steps must be immediately taken or: elsea non-uniform yarn-bundle will "result. The procedureusuallyfollowedxis. that of wiping. In other words,- the" spinneret."face is wiped. clean in the hope that all the holes will. commencespinning uniformly." ,F quean this, must, be done several"times 'bforespin 'ingxprooeeds in the' proper v manner; and]: con u'e'nny'er'itail'sfa considerable loss: of production as wellflas" addinganother operation} j. T

A principal ob J'ect 'cijth'is invention", therefore, is'to'seciireffrom'theistartfof a dry or'meltr s inning operationsimultaneous and uniform extrusionsiiromall holes'l f multi hole'spinner'ets'. Another-obj ec't. is to providesimme, inexpensive meansfor securing'fa satisfactory start-up ofIa conventional 'dryjor'melt-spinning operation. other objects j will more clearly a pear"herein.- after.

Theseobje'ct's are, realized by the pr'e'sent inl- "verition 'ivl iicli,briefly stated, comprises. provid-v ing the multi-liqlespinneret, beforeth e S inning operationisinitiated, with a rupturable barrier plajc'edincontact with the inner or outer face of the spinneret and sized to coveror close all of the'fholes of thespinnerti whereby to permitb'a'ckpressuifeto piat 'the' inner face ofthe. spin neiet'" and hence causethe,'spinning imaterialto be distributed uniformly overthejback face ofthe spinnere'tQ Gradually, the back pressurereaches a point'where thebarrier ruptures" at all. spine neretfholes, simultaneouslmfthusinsuring suffe 'fi'cie'nt pressure iortheimmediate and uniformextrusipnfof 'spinningiinaterial' through all, of said'h oles. I g I A nThe rupturable'barrie'r utilizedfin accordance with the principles ofthisinvention'may be of any convenient fi1m Ql"fOl1-WhlCh will withstandthe operating temperatures encountered in the spinning head; Asisuitable 1 "examples of metals from which" these "rupturabie barriers" mbe prepared, "the 'foll'oWing"-"'ma'y be mentioned? ammimim; beryllium,chromium, copper; gold; iron} magnesiumf nickelj'platinum z'ir'icfjetci,and various alloy'sj th reofi'; n th' c' ecrmateriai that are spun at-re anve1y 1ow temperatures, suitalile barriers may be pre aredfrom'yarious film-forming polymeric materials? As fsuitable examples;are films repared'rmm poly-amides and fpolyesteis aswell a's --'variousvinyl polymers suclras polyacrylonitrile; vinylidene chloride, etc;

3 In addition, films prepared from cellulose esters and regeneratedcellulose may be used for many such applications. However, for hightemperature applications, e. g. such as those encountered in the meltspinning of polyamides, metallic barriers will normally be preferred.

The main requirement with regard to operativeness is that the foilshould be thin enough so that it will rupture when the back pressure hasreached that which is normally encountered in the spinning operation,thus insuring that abnormal back pressures are not built up. Suitablethicknesses for such foils may vary from 0.0001 inch to 0.01 inch,depending upon the material used in making the film. As a method fordetermining the correct thickness of the film to be used, the followingequation serves to givea useful approximation:

wherein:

t=thickness of film or foil (inches) P=operating back pressure (poundsper square inch) R=radius of spinneret aperture (inches) a=teI1Si1estrength of film or foil at operating temperature (pounds per squareinch) Although the rupturable barrier may be placed at either the frontor back face of the spinneret, in most instances, and particularly wherea metal foil is to used, it will be found most convenient to positionthe rupturable barrier over the back (inner) face of the spinneret.Alternatively a suitable barrier may be formed by coating the outerfaceof the spinneret with an appropriate filmformer of the type hereinabovementioned, or a. barrier of film or foil may be cemented to the frontface of the spinneret or secured thereon by any one of a number ofconventional clamping expedients, e. g. a contractible band fittedaround the outer side wall of the spinneret. In the case of the recessedtype spinneret wherein a filter pack is placed directly against the backface of the spinneret, e. g. dry-spinning of cellulose acetate, the filmor foil may be conveniently used across the polymer supply side of thefilter pack. Here again, the primary purpose is served. 1. e. thespinning material is distributed evenly over the area of the pack andspinneret, causing pack compression before the film bursts, thusinsuring uniform extrusion.

The principles and practice of the invention are further illustrated bythe following examplesof preferred embodiments, reference being had tothe accompanying drawing wherein is shown, diagrammatically, a typicalsystem involving the use of the novel rupturable barrier of thisinvention. Legends in the description refer to like parts in thedrawing.

Example I A melt pool I containing molten polyhexa-- methylene adipamideis maintained in the vicinityof 280 C. The molten polymer is forced by asuitable pump 2 through a sand pack filter 3 to the spinneret 4. Acrossthe back face of the spinneret, there is a rupturable barrier 5comprising an aluminum foil 0.001 inch in thickness. The spinneretitself is a 70-hole spinneret 3 inches in diameter, each hole being0.00? inch in diameter. The aluminum foil barrier causes the backpressure within the pack and polymer supply line to build up until it issuflicient to rupture 4 the aluminum foil at each point of non-support,i. e. the individual spinneret holes. When the pressure is sufiicient todo this, holes are burst in the foil by the back pressure and uniformextrusion through all the holes of the spinneret occurs. Using theprocess of this invention with this type spinneret in the spinning of 3denier per filament staple, fifteen out of twenty successful starts wereachieved. For comparison, when the start-up procedure was tried withoutusing a rupturable barrier, it was only possible to achieve twentysuccessful starts out of fortythree tries.

Example II In a procedure, as in Example I, a 0.001 inch thick aluminumfoil is used in the starting up of a spinneret 4% inches in diametercontaining 200 holes, each 0.007 inch in diameter, for the spinning of 1A, denier per filament staple. Using the same procedure as outlined inExample I, three successful starts out of four tries are achieved usingthe aluminum foil. For comparative purposes, without the use of aluminumfoil, only one successful start out of five tries is obtained.

Emample III This same procedure is repeated using the apparatusdescribed in Example II, but substituting in the place of the aluminumfoil 0.00025 inch thick nickel foil. Here again, a considerableimprovement in start-up performance is achieved. Out of ten tries, sevensuccessful start-ups are obtained. For comparison, without the use ofthe foil, in ten tries only five successful start-ups are realized.

As many apparently widely different embodiments can be made withoutdeparting from the spirit and scope of my invention, it is to beunderstood that said invention is not limited in any Way except as setforth in the appended claims.

I claim:

1. In the process of spinning filaments, yarns and threads of syntheticfilament-forming materials wherein a spinning composition comprisingsynthetic filament-forming material is extruded through a multi-holespinneret into a gaseous atmosphere, the improvement which comprisescovering the holes of the spinneret, prior to spinning, with arupturable barrier of sufficient thickness to prevent the extrusion ofspinning composition through the holes of said spinneret only until thepressure of spinning composition over the inner face of the spinnerethas reached the level customarily encountered in the spinning operation,at which point the barrier ruptures at substantially all holes of thespinneret simultaneously to permit extrusion of spinning compositiontherethrough, and thereafter forcing spinning composition into saidspinneret whereby to rupture said barrier and initiate spinning.

2. In the process of spinning filaments, yarns and threads of syntheticfilament-forming materials wherein a spinning composition comprisingsynthetic filament-forming material is extruded through a multi-holespinneret into a gaseous atmosphere, the improvement which comprisescovering the inner face of the spinneret, prior to spinning, with arupturable barrier of suflicient thickness to prevent the extrusion ofspinning composition through the holes of the spinneret only until thepressure of spinning composition over the inner face of the spinnerethas reached the level ordinarily encountered in the 5 spinningoperation, at which point the barrier ruptures at substantially all theholes of the spinneret to permit extrusion of spinning compositiontherethrough, and thereafter forcing spinning composition into saidspinneret whereby to rupture said barrier and initiate spinning.

3. A multi-hole spinneret, the holes of which are covered by arupturable barrier of a thickness to prevent spinning solution frompassing through said holes only until the back pressure in saidspinneret reaches the level ordinarily encountered in the normaloperation of said spinneret.

4. A multi-hole spinneret, the inner face of which is substantiallycovered with an impervious barrier whereby to close the holes of saidspinneret, said barrier being of a thickness to prevent No referencescited.

